There is no clear dividing line between engineering plastics and general-purpose plastics. For example, acrylonitrile-butadiene-styrene copolymer (ABS) lies between the two. Its advanced grades can be used as engineering structural materials. The grade is ordinary general-purpose plastics (abroad generally speaking, ABS is classified as general-purpose plastics). For another example, polypropylene (PP) is a typical general-purpose plastic, but after glass fiber reinforcement and other blending, its mechanical strength and heat resistance have been greatly improved, and it can also be used as a structural material in many engineering fields . For another example, polyethylene is also a typical general-purpose plastic, but ultra-high molecular weight polyethylene with a molecular weight of more than 1 million, due to its excellent mechanical properties and high heat distortion temperature, can be widely used as engineering plastics in machinery, transportation, Chemical equipment etc.